Contamination barrier with expandable lamellas

ABSTRACT

A contamination barrier that passes through radiation from a radiation source and captures debris coming from the radiation source is disclosed. The contamination barrier includes an inner ring, an outer ring, and a plurality of lamellas. The lamellas extend in a radial direction from a main axis, and each of the lamellas is positioned in a respective plane that include the main axis. At least one outer end of each of the lamellas is slidably connected to at least one of the inner and outer ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priorityfrom European Patent Application No. 0280454.8, filed Dec. 23, 2003, andEuropean Patent Application No. 03075086.3, filed Jan. 13, 2003, thecontents of which are both incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates generally to a lithographic apparatus, andmore specifically to a contamination barrier for passing throughradiation from a radiation source and for capturing debris coming fromthe radiation source.

[0004] 2. Description of Related Art

[0005] A contamination barrier for a lithographic apparatus is knownfrom, for example, the international patent application WO 02/054153.The contamination barrier is normally positioned in a wall between twovacuum chambers of a radiation system of a lithographic projectionapparatus.

[0006] In a lithographic projection apparatus, the size of features thatcan be imaged onto a substrate is limited by the wavelength ofprojection radiation. To produce integrated circuits with a higherdensity of devices, and hence higher operating speeds, it is desirableto be able to image smaller features. While most current lithographicprojection apparatus employ ultraviolet light generated by mercury lampsor excimer lasers, it has been proposed to use shorter wavelengthradiation in the range 5 to 20 nm, especially around 13 nm. Suchradiation is termed extreme ultraviolet (EUV), or soft x-ray, andpossible sources include, for example, laser-produced plasma sources,discharge plasma sources, or synchrotron radiation from electron storagerings. Apparatus using discharge plasma sources are described in: W.Partlo, I. Fomenkov, R. Oliver, D. Birx, “Development of an EUV (13.5nm) Light Source Employing a Dense Plasma Focus in Lithium Vapor”, Proc.SPIE 3997, pp. 136-156 (2000); M. W. McGeoch, “Power Scaling of aZ-pinch Extreme Ultraviolet Source”, Proc. SPIE 3997, pp. 861-866(2000); W. T. Silfvast, M. Klosner, G. Shimkaveg, H. Bender, G. Kubiak,N. Fornaciari, “High-Power Plasma Discharge Source at 13.5 and 11.4 nmfor EUV lithography”, Proc. SPIE 3676, pp. 272-275 (1999); and K.Bergmann et al., “Highly Repetitive, Extreme Ultraviolet RadiationSource Based on a Gas-Discharge Plasma”, Applied Optics, Vol.38, pp.5413-5417 (1999).

[0007] EUV radiation sources may require the use of a rather highpartial pressure of a gas or vapor to emit EUV radiation, such asdischarge plasma radiation sources referred to above. In a dischargeplasma source, for example, a discharge is created between electrodes,and a resulting partially ionized plasma may subsequently be caused tocollapse to yield a very hot plasma that emits radiation in the EUVrange. The very hot plasma is quite often created in Xe, since a Xeplasma radiates in the Extreme UV (EUV) range around 13.5 nm. For anefficient EUV production, a typical pressure of 0.1 mbar is requirednear the electrodes to the radiation source. A drawback of having such arather high Xe pressure is that Xe gas absorbs EUV radiation. Forexample, 0.1 mbar Xe transmits over 1 m only 0.3% EUV radiation having awavelength of 13.5 nm. It is therefore required to confine the ratherhigh Xe pressure to a limited region around the source. To reach this,the source can be contained in its own vacuum chamber that is separatedby a chamber wall from a subsequent vacuum chamber in which thecollector mirror and illumination optics may be obtained. The chamberwall can be made transparent to EUV radiation by a number of aperturesin the wall provided by a contamination barrier or so-called “foiltrap,” such as the one described in European Patent application numberEP-A-1 057 079, which is incorporated herein by reference. In EP-A-1 057079 a foil trap has been proposed to reduce the number of particlespropagating along with the EUV radiation. This foil trap consists of anumber of lamella shaped walls, which are close together in order toform a flow resistance, but not too close so as to let the radiationpass without substantially obstructing it. The lamellas can be made ofvery thin metal platelets, and are positioned near the radiation source.The lamellas are positioned in such a way, that diverging EUV radiationcoming from a radiation source, can easily pass through, but debriscoming from the radiation source is captured. Debris particles collidewith gas inside the foil trap, are scattered thereby, and eventuallycollide with the lamellas and stick to these lamellas.

[0008] The lamellas, however, absorb some EUV radiation and heat.Moreover, they are heated by colliding debris particles. This results insignificant heating of the lamellas and a supporting structure whichsupports the lamellas. Since optical transmission is very important in alithographic projection apparatus, mechanical deformation is notallowed.

SUMMARY OF THE INVENTION

[0009] Therefore, it is an aspect of the present invention to provide acontamination barrier in which disadvantageous deformation of lamellasis minimized.

[0010] It is another aspect of embodiments of the present invention toprovide a foil trap for a lithographic projection apparatus. The foiltrap forms an open structure to let radiation coming from, for example,an EUV source, pass unhindered. The foil trap comprises lamellasarranged to capture debris particles coming from the radiation source.The lamellas are extending in a radial direction from a foil trap axis.In order to prevent mechanical stress, the lamellas are slidablyconnected in grooves of one or both of the rings. In this way, thelamellas can expand easily and mechanical stress is avoided, so thatthere is no deformation of the lamellas. At least one of the outer endsof the lamellas is thermally connected to a ring. This ring may becooled by a cooling system. In a preferred embodiment, the foil trapcomprises a shield to protect the inner ring from being hit by the EUVbeam.

[0011] This aspect is achieved according to embodiments of the presentinvention by a contamination barrier. The contamination barriercomprises a number of lamellas extending in a radial direction from amain axis, each of the lamellas being positioned in a plane thatcontains the main axis, characterized in that the contamination barriercomprises an inner ring and an outer ring and that each of the lamellasis slidably positioned at least one of its outer ends in grooves of atleast one of the inner and outer ring.

[0012] Embodiments also provide for a contamination barrier that passesthrough radiation from a radiation source and captures debris comingfrom the radiation source. The contamination barrier includes an innerring, an outer ring, and a plurality of lamellas that extend in a radialdirection from a main axis. Each of the lamellas is positioned in arespective plane that includes the main axis. At least one outer end ofeach of the lamellas is slidably connected to at least one of the innerand outer ring.

[0013] Embodiment of the invention further provide for a contaminationbarrier that passes through radiation from a radiation source andcaptures debris coming from the radiation source. The contaminationbarrier includes a plurality of lamellas, and a support structure thatslidably engages the lamellas. The lamellas and the support structureare configured and arranged to allow the lamellas to expand and contractin response to changes in temperature.

[0014] Embodiment of the invention also provide for a contaminationbarrier that permits radiation to pass therethrough and captures debrisfrom a radiation source generated by the radiation source. Thecontamination barrier includes a support structure and a plurality ofthin plate members mounted on the support structure. The radiationpropagates along an optical axis and the thin plate members are disposedalong a plane that includes the axis. The plate members are slidablymovable relative to the support structure.

[0015] By slidably positioning one of the outer ends of a lamella, thelamella can expand in a radial direction without the appearance ofmechanical tension which may create a deformation of the lamella.

[0016] Preferably, the lamellas are thermally connected to at least oneof the inner and outer ring. In this way, heat from the lamellas will betransported to the rings. Note that a thermal connection is notnecessarily a mechanical connection; heat conduction from the lamellasto the rings is even possible when the connection is slidable.Furthermore, a connection using a heat conducting gel between thelamellas and the rings is possible.

[0017] In an embodiment, the contamination barrier comprises a firstshield arranged to protect the inner ring from being hit by radiationfrom the radiation source. In this way, the heating of the inner ring islimited. Preferably, the contamination barrier comprises a second shieldarranged to block thermal radiation from the first shield. By blockingthe heat radiation coming from the first heat shield, the beam goinginto the collector is not exposed by unwanted radiation.

[0018] In a further embodiment, upstream of the first shield, withrespect to the direction of propagation of the radiation emitted by theradiation source along the main axis, a third shield is provided,constructed and arranged to reduce heating of the first shield caused bydirect radiation from the radiation source. The third shield preventsthe first shield from being excessively heated by direct radiation fromthe radiation source, and consequently further reduces heat radiatingfrom the first shield towards the collector.

[0019] In a preferred embodiment, the contamination barrier alsocomprises at least one cooling spoke to support the first shield,wherein the cooling spoke is thermally connected to the outer ring. Thecooling spoke can be made of metal or any other heat conductivematerial, such as carbon. The cooling spoke not only supports the firstshield, but also transports heat from the first heat shield to the outerring.

[0020] In an embodiment, the first shield comprises a number of shieldmembers, each shield member being connected to the outer ring via aseparate cooling spoke.

[0021] In a further embodiment, the contamination barrier comprises afirst cooling device or structure that is arranged to cool at least oneof the first and second shield. In this case, a cooling spoke asdescribed above is not necessary. The cooling device may comprise acooling system in which a cooling fluid is used to remove the heat awayfrom the contamination barrier. The cooling device may be part of acooling system used in a collector. In this way, the cooling device willbe in the shadow of the heat shields, and thus not blocking the EUVradiation beam. Preferably, the heat shields are supported by thecooling device. Vibrations coming from the cooling system will not reachthe lamellas of the contamination barrier because the inner ring is notfixed to the cooling system.

[0022] In yet another embodiment, the contamination barrier comprises asecond cooling device arranged to cool the inner ring. If the coolingring is cooled directly, there will be no need for a heat shield.

[0023] In a further embodiment, the contamination barrier comprises athird cooling device arranged to cool the outer ring. If the lamellasare slidably connected to the inner ring and thermally connected to theouter ring, the heat form the lamellas will go to the outer ring. Theouter ring can be easily cooled by for example water cooling, since itis outside the EUV optical path.

[0024] Preferably, the lamellas are curved in the respective planes, andthe inner and outer ring are shaped as slices of a conical pipe. If thesurfaces of the outer and inner ring are focused on the EUV source, theEUV beam will be blocked by the rings as little as possible. Only theinner ring will be in the way for the EUV beam, which is unavoidable.However, no light is lost, as the collector is unable to collectradiation in this solid angle anyway.

[0025] In a further embodiment, a first side of the lamellas, at leastin use facing the radiation source, is thicker than the rest of thelamellas. In this way, the influence of minor warping of the lamellas isreduced. The warped lamellas should be positioned in the shadow of thethick front side of the lamellas. This measure results in betteruniformity of the transmission of the contamination barrier.

[0026] The present invention also relates to a radiation systemcomprising a contamination barrier as described above, and a collectorfor collecting radiation passing the contamination barrier.

[0027] It is another aspect of the present invention to extend thelifetime of a collector of a radiation system. Therefore, embodiments ofthe invention relate to a radiation system comprising: a contaminationbarrier for passing through radiation from a radiation source and forcapturing debris coming from the radiation source, the contaminationbarrier comprising a number of lamellas, and a collector for collectingradiation passing the contamination barrier, characterized in that asurface of the lamellas is covered with the same material as an opticalsurface of the collector.

[0028] Embodiments also provide a radiation system that includes acontamination barrier that passes through radiation from a radiationsource and captures debris coming from the radiation source, and acollector that collects radiation passing the contamination barrier. Thecontamination barrier includes an inner ring, an outer ring, and aplurality of lamellas that extend in a radial direction from a mainaxis. Each of the lamellas is positioned in a respective plane thatincludes the main axis, and at least one outer end of each of thelamellas is slidably connected to at least one of the inner and outerring.

[0029] Another embodiment includes a radiation system that includes acontamination barrier that passes through radiation from a radiationsource and captures debris coming from the radiation source, and acollector that collects radiation passing the contamination barrier. Thecontamination barrier includes a plurality of lamellas, and a surface ofthe lamellas is covered with the same material as an optical surface ofthe collector.

[0030] When material is sputtered off of the contamination barrier ontothe collector, the life time of the collector is only minimallyinfluenced if the materials are equal.

[0031] Embodiments of the invention also relate to a lithographicprojection apparatus comprising: a support structure constructed andarranged to hold a patterning device, to be irradiated by a projectionbeam of radiation to pattern the projection beam of radiation, asubstrate table constructed and arranged to hold a substrate, and aprojection system constructed and arranged to image an irradiatedportion of the patterning device onto a target portion of the substrate,wherein the projection apparatus comprises a radiation system forproviding a projection beam of radiation as described above.

[0032] A further embodiment is directed to a lithographic projectionapparatus. The lithographic projection apparatus includes a radiationsystem to provide a beam of radiation, a support structure to support apatterning structure to be irradiated by a beam of radiation to patternsaid beam of radiation, a substrate support to support a substrate, anda projection system to image an irradiated portion of the patterningstructure onto a target portion of the substrate. The radiation systemincludes a contamination barrier that passes through radiation from aradiation source and captures debris coming from the radiation sourceand a collector for collecting radiation passing the contaminationbarrier. The contamination barrier includes an inner ring, an outerring, and a plurality of lamellas that extend in a radial direction froma main axis. Each of the lamellas is positioned in a respective planethat includes the main axis, and each of the lamellas is slidablyconnected to at least one of the inner and outer ring.

[0033] Yet another embodiment is directed to a lithographic projectionapparatus that includes a radiation system to provide a beam ofradiation, a support structure to support a patterning structure to beirradiated by a beam of radiation to pattern the beam of radiation, asubstrate support to support a substrate; and a projection system toimage an irradiated portion of the patterning structure onto a targetportion of the substrate. The radiation system includes a contaminationbarrier that passes through radiation from a radiation source andcaptures debris coming from the radiation source, and a collector thatcollects radiation passing the contamination barrier. The contaminationbarrier includes a plurality of lamellas, wherein a surface of thelamellas is covered with the same material as an optical surface of thecollector.

[0034] Another embodiment is directed to a method of manufacturing anintegrated structure by a lithographic process. The method includesradiating a beam of radiation through a radiation system, providing asupport structure to support a patterning structure to be irradiated bythe beam of radiation to pattern said beam of radiation, providing asubstrate support to support a substrate, and providing a projectionsystem to image an irradiated portion of the patterning structure onto atarget portion of the substrate. Radiating the beam of radiation throughthe radiation system includes passing radiation from a radiation sourcethrough a contamination barrier comprising an inner ring, an outer ring,and a plurality of lamellas extending in a radial direction from a mainaxis. Each of the lamellas are positioned in a respective plane thatcomprises the main axis, and at least one outer end of each of thelamellas is slidably connected to at least one of the inner and outerring. Radiating the beam of radiation also includes collecting radiationpassing the contamination barrier.

[0035] Embodiments of the invention also relate to a method ofmanufacturing an integrated structure by a lithographic process. Themethod includes radiating a beam of radiation through a radiationsystem, providing a support structure to support a patterning structureto be irradiated by the beam of radiation to pattern said beam ofradiation, providing a substrate support to support a substrate, andproviding a projection system to image an irradiated portion of thepatterning structure onto a target portion of the substrate. Radiatingthe beam of radiation through the radiation system includes passingradiation from a radiation source through a contamination barrier thatincludes a plurality of lamellas, capturing debris from the radiationsource, and collecting radiation passing the contamination barrier. Asurface of the lamellas is covered with the same material as an opticalsurface of the collector.

[0036] Embodiments of the invention are also directed to a method ofmanufacturing an integrated structure by a lithographic process. Themethod includes generating a beam of radiation with a radiation source,capturing debris from the radiation source, collecting radiation passingthe contamination barrier patterning the beam of radiation with apatterning structure, and imaging an irradiated portion of thepatterning structure onto a target portion of a substrate. Capturingdebris comprises providing a support structure and a plurality oflamellas that are slidably engaged with the support structure so as toallow the plurality of lamellas to expand and contract in response tochanges in temperature.

[0037] The term “patterning device” as here employed should be broadlyinterpreted as referring to a device that can be used to endow anincoming radiation beam with a patterned cross-section, corresponding toa pattern that is to be created in a target portion of the substrate;the term “light valve” can also be used in this context. Generally, thepattern will correspond to a particular functional layer in a devicebeing created in the target portion, such as an integrated circuit orother device (see below). Examples of such patterning devices include:

[0038] A mask. The concept of a mask is well known in lithography, andit includes mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. Placementof such a mask in the radiation beam causes selective transmission (inthe case of a transmissive mask) or reflection (in the case of areflective mask) of the radiation impinging on the mask, according tothe pattern on the mask. In the case of a mask, the support structurewill generally be a mask table, which ensures that the mask can be heldat a desired position in the incoming radiation beam, and that it can bemoved relative to the beam if so desired;

[0039] A programmable mirror array. One example of such a device is amatrix-addressable surface having a viscoelastic control layer and areflective surface. The basic principle behind such an apparatus is that(for example) addressed areas of the reflective surface reflect incidentlight as diffracted light, whereas unaddressed areas reflect incidentlight as undiffracted light. Using an appropriate filter, theundiffracted light can be filtered out of the reflected beam, leavingonly the diffracted light behind; in this manner, the beam becomespatterned according to the addressing pattern of the matrix-addressablesurface. An alternative embodiment of a programmable mirror arrayemploys a matrix arrangement of tiny mirrors, each of which can beindividually tilted about an axis by applying a suitable localizedelectric field, or by employing a piezoelectric actuation device. Onceagain, the mirrors are matrix-addressable, such that addressed mirrorswill reflect an incoming radiation beam in a different direction tounaddressed mirrors; in this manner, the reflected beam is patternedaccording to the addressing pattern of the matrix-addressable mirrors.The required matrix addressing can be performed using suitableelectronic means. In both of the situations described hereabove, thepatterning device can comprise one or more programmable mirror arrays.More information on mirror arrays as here referred to can be gleaned,for example, from U.S. Pat. No. 5,296,891 and U.S. Pat. No. 5,523,193,and PCT patent applications WO 98/38597 and WO 98/33096, which areincorporated herein by reference. In the case of a programmable mirrorarray, the support structure may be embodied as a frame or table, forexample, which may be fixed or movable as required; and

[0040] A programmable LCD array. An example of such a construction isgiven in U.S. Pat. No. 5,229,872, which is incorporated herein byreference. As above, the support structure in this case may be embodiedas a frame or table, for example, which may be fixed or movable asrequired.

[0041] For purposes of simplicity, the rest of this text may, at certainlocations, specifically direct itself to examples involving a mask andmask table; however, the general principles discussed in such instancesshould be seen in the broader context of the patterning device ashereabove set forth.

[0042] Lithographic projection apparatus can be used, for example, inthe manufacture of integrated circuits (ICs). In such a case, thepatterning device may generate a circuit pattern corresponding to anindividual layer of the IC, and this pattern can be imaged onto a targetportion (e.g. comprising one or more dies) on a substrate (siliconwafer) that has been coated with a layer of radiation-sensitive material(resist). In general, a single wafer will contain a whole network ofadjacent target portions that are successively irradiated via theprojection system, one at a time. In current apparatus, employingpatterning by a mask on a mask table, a distinction can be made betweentwo different types of machine. In one type of lithographic projectionapparatus, each target portion is irradiated by exposing the entire maskpattern onto the target portion in one go; such an apparatus is commonlyreferred to as a wafer stepper or step and repeat apparatus. In analternative apparatus—commonly referred to as a step and scanapparatus—each target portion is irradiated by progressively scanningthe mask pattern under the projection beam in a given referencedirection (the “scanning” direction) while synchronously scanning thesubstrate table parallel or anti parallel to this direction; since, ingeneral, the projection system will have a magnification factor M(generally<1), the speed V at which the substrate table is scanned willbe a factor M times that at which the mask table is scanned. Moreinformation with regard to lithographic devices as here described can begleaned, for example, from U.S. Pat. No. 6,046,792, incorporated hereinby reference.

[0043] In a manufacturing process using a lithographic projectionapparatus, a pattern (e.g. in a mask) is imaged onto a substrate that isat least partially covered by a layer of radiation sensitive material(resist). Prior to this imaging step, the substrate may undergo variousprocedures, such as priming, resist coating and a soft bake. Afterexposure, the substrate may be subjected to other procedures, such as apost exposure bake (PEB), development, a hard bake andmeasurement/inspection of the imaged features. This array of proceduresis used as a basis to pattern an individual layer of a device, e.g. anIC. Such a patterned layer may then undergo various processes such asetching, ion implantation (doping), metallization, oxidation, chemomechanical polishing, etc., all intended to finish off an individuallayer. If several layers are required, then the whole procedure, or avariant thereof, will have to be repeated for each new layer.Eventually, an array of devices will be present on the substrate(wafer). These devices are then separated from one another by atechnique such as dicing or sawing, whence the individual devices can bemounted on a carrier, connected to pins, etc. Further informationregarding such processes can be obtained, for example, from the book“Microchip Fabrication: A Practical Guide to Semiconductor Processing”,Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN0 07 067250 4, incorporated herein by reference.

[0044] For the sake of simplicity, the projection system may hereinafterbe referred to as the “lens”; however, this term should be broadlyinterpreted as encompassing various types of projection system,including refractive optics, reflective optics, and catadioptricsystems, for example. The radiation system may also include componentsoperating according to any of these design types for directing, shapingor controlling the projection beam of radiation, and such components mayalso be referred to below, collectively or singularly, as a “lens”.Further, the lithographic apparatus may be of a type having two or moresubstrate tables (and/or two or more mask tables). In such “multiplestage” devices the additional tables may be used in parallel, orpreparatory steps may be carried out on one or more tables while one ormore other tables are being used for exposures. Dual stage lithographicapparatus are described, for example, in U.S. Pat. No. 5,969,441 and WO98/40791, both incorporated herein by reference.

[0045] Although specific reference may be made in this text to the useof the apparatus according to the invention in the manufacture of ICs,it should be explicitly understood that such an apparatus has many otherpossible applications. For example, it may be employed in themanufacture of integrated optical systems, guidance and detectionpatterns for magnetic domain memories, liquid crystal display panels,thin film magnetic heads, etc. The skilled artisan will appreciate that,in the context of such alternative applications, any use of the terms“reticle”, “wafer” or “die” in this text should be considered as beingreplaced by the more general terms “mask”, “substrate” and “targetportion”, respectively.

[0046] In the present document, the terms “radiation” and “beam” areused to encompass all types of electromagnetic radiation, includingultraviolet (UV) radiation (e.g. with a wavelength of 365, 248, 193, 157or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having awavelength in the range 5-20 nm), as well as particle beams, such as ionbeams or electron beams.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Embodiments of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

[0048]FIG. 1 schematically depicts a lithographic projection apparatusaccording to embodiments of the present invention;

[0049]FIG. 2 shows a side view of a part of the apparatus of FIG. 1 inan embodiment, i.e., an EUV illuminating system and projection optics;

[0050]FIG. 3 shows a foil trap with an inner and outer ring, andlamellas according to an embodiment of the invention;

[0051]FIG. 4 shows a foil trap with a cooling spoke and a heat shieldaccording to an embodiment of the invention;

[0052]FIG. 5 is a 3-D picture of an inner ring according to anembodiment of the invention;

[0053]FIG. 6 shows a detailed example of a lamella of a foil trapaccording to an embodiment of the invention;

[0054]FIG. 7 shows a foil trap with a cooling spoke and two heatshields; and

[0055]FIG. 8 shows alternative embodiment of a foil trap with a coolingspoke and two heat shields.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0056]FIG. 1 schematically depicts a lithographic projection apparatus 1according to a particular embodiment of the invention. The apparatuscomprises: a radiation system Ex, IL, for supplying a projection beam PBof radiation (e.g. EUV radiation) with a wavelength of 11-14 nm. In thisparticular case, the radiation system also comprises a radiation sourceLA; a first object table (mask table) MT provided with a mask holder forholding a mask MA (e.g. a reticle), and connected to a first positioningdevice PM for accurately positioning the mask with respect to item PL; asecond object table (substrate table) WT provided with a substrateholder for holding a substrate W (e.g. a resist coated silicon wafer),and connected to a second positioning device PW for accuratelypositioning the substrate with respect to item PL; and a projectionsystem (“lens”) PL for imaging an irradiated portion of the mask MA ontoa target portion C (e.g. comprising one or more dies) of the substrateW. The term “object table” as used herein can also be considered ortermed as an object support. It should be understood that the termobject support or object table broadly refers to a structure thatsupports, holds, or carries an object, such as a mask or a substrate.

[0057] As here depicted, the apparatus is of a reflective type (i.e. hasa reflective mask). However, in general, it may also be of atransmissive type, for example (with a transmissive mask).Alternatively, the apparatus may employ another kind of patterningdevice, such as a programmable mirror array of a type as referred toabove.

[0058] The source LA (e.g. a laser-produced plasma or a discharge plasmaEUV radiation source) produces a beam of radiation. This beam is fedinto an illumination system (illuminator) IL, either directly or afterhaving traversed conditioning means, such as a beam expander Ex, forexample. The illuminator IL may comprise an adjusting device AM forsetting the outer and/or inner radial extent (commonly referred to asσ-outer and σ-inner, respectively) of the intensity distribution in thebeam. In addition, it will generally comprise various other components,such as an integrator IN and a condenser CO, see FIG. 1. In this way,the beam PB impinging on the mask MA has a desired uniformity andintensity distribution in its cross section.

[0059] It should be noted with regard to FIG. 1 that the source LA maybe within the housing of the lithographic projection apparatus (as isoften the case when the source LA is a mercury lamp, for example), butthat it may also be remote from the lithographic projection apparatus,the radiation beam which it produces being led into the apparatus (e.g.with the aid of suitable directing mirrors). This latter scenario isoften the case when the source LA is an excimer laser. Embodiments ofthe current invention, and claims, encompass both of these scenarios.

[0060] The beam PB subsequently intercepts the mask MA, which is held ona mask table MT. Having traversed the mask MA, the beam PB passesthrough the lens PL, which focuses the beam PB onto a target portion Cof the substrate W. With the aid of the second positioning device PW(and an interferometric measuring device IF), the substrate table WT canbe moved accurately, e.g. so as to position different target portions Cin the path of the beam PB. Similarly, the first positioning device PMcan be used to accurately position the mask MA with respect to the pathof the beam PB, e.g. after mechanical retrieval of the mask MA from amask library, or during a scan. In general, movement of the objecttables MT, WT will be realized with the aid of a long-stroke module(coarse positioning) and a short-stroke module (fine positioning), whichare not explicitly depicted in FIG. 1. However, in the case of a waferstepper (as opposed to a step-and-scan apparatus) the mask table MT mayjust be connected to a short stroke actuator, or may be fixed. Mask MAand substrate W may be aligned using mask alignment marks M1, M2 andsubstrate alignment marks P1, P2.

[0061] The depicted apparatus can be used in two different modes:

[0062] 1. In step mode, the mask table MT is kept essentiallystationary, and an entire mask image is projected in one go (i.e. asingle “flash”) onto a target portion C. The substrate table WT is thenshifted in the x and/or y directions so that a different target portionC can be irradiated by the beam PB; and

[0063] 2. In scan mode, essentially the same scenario applies, exceptthat a given target portion C is not exposed in a single “flash”.Instead, the mask table MT is movable in a given direction (the socalled “scan direction”, e.g. the y direction) with a speed ν, so thatthe projection beam PB is caused to scan over a mask image;concurrently, the substrate table WT is simultaneously moved in the sameor opposite direction at a speed V=Mν, in which M is the magnificationof the projection system PL (typically, M=¼ or ⅕). In this manner, arelatively large target portion C can be exposed, without having tocompromise on resolution.

[0064]FIG. 2 shows an embodiment of the lithographic projectionapparatus 1 of FIG. 1, comprising a radiation system 3 (i.e.“source-collector module”), an illumination optics unit 4, and theprojection system PL. The radiation system 3 is provided with aradiation source LA which may comprise a discharge plasma source. Theradiation source LA may employ a gas or vapor, such as Xe gas or Livapor in which a very hot plasma can be created to emit radiation in theEUV range of the electromagnetic spectrum. The very hot plasma iscreated by causing a partially ionized plasma of an electrical dischargeto collapse onto an optical axis 20. Partial pressures of 0.1 mbar of Xegas, Li vapor or any other suitable gas or vapor may be required forefficient generation of the radiation. The radiation emitted by theradiation source LA is passed from a source chamber 7 into a collectorchamber 8 via a foil trap 9. The foil trap 9 comprises a channelstructure such as, for example, described in detail in European patentapplication EP-A-1 057 079, which is incorporated herein by reference.The term “foil trap” as used herein can also be considered or termed acontamination barrier. It should be understood that the term foil trapor contamination barrier broadly refers to a structure that capturesdebris coming from the radiation source LA.

[0065] The collector chamber 8 comprises a radiation collector 10 whichmay be formed by a grazing incidence collector. Radiation passed by theradiation collector 10 is reflected off a grating spectral filter 11 ormirror to be focused in a virtual source point 12 at an aperture in thecollector chamber 8. From chamber 8, the projection beam 16 is reflectedin the illumination optics unit 4 via normal incidence reflectors 13, 14onto a reticle or mask positioned on reticle or mask table MT. Apatterned beam 17 is formed which is imaged in projection optics systemPL via reflective elements 18, 19 onto wafer stage or substrate tableWT. More elements than shown may generally be present in illuminationoptics unit 4 and projection system PL.

[0066]FIG. 3 shows a downstream and a cross-sectional view,respectively, of a foil trap 9 with a plurality of lamellas 31, 32according to an embodiment of the invention. The foil trap 9 comprisesan inner ring 33 and an outer ring 35. Preferably, the inner ring 33 andthe outer ring 35 are shaped as slices of a conical pipe, wherein aminimum diameter d_(o) of the outer ring 35 is larger than a minimumdiameter d_(i) of the inner ring 33. Preferably, both conical rings 33,35 share the same main axis 34 and focus. Preferably, the foil trap 9 isarranged in a lithographic projection apparatus, in such a way that themain axis 34 of the foil trap 9 and the optical axis 20 of the radiationsystem 3 coincide, see FIG. 2.

[0067] In FIG. 4, the foil trap 9, as shown, comprises a heat shield 41.The heat shield 41 is supported by two cooling spokes 44, 45 which aremechanically and thermally connected to the outer ring 35. At the centerof the foil trap 9, the cooling spokes 44, 45 connect to a spindle 47,which supports the heat shield 41. The heat shield 41 comprises a disk,which avoids the inner ring 33 from being hit by the emitted radiationand heat from the radiation source LA. In this way, the heat shield 41shields off the inner ring 33. The cooling spokes 44, 45, the spindle 47and the heat shield 41 are preferably made of a good heat conductor. Inthis way, heat developed on the heat shield 41, may easily betransferred to the outer ring 35 via the cooling spokes 44, 45.

[0068] Alternatively, the heat shield 41 may comprise two (or more) discparts, each disc part being connected to one cooling spoke 44, 45. Inthis case, the spindle 47 will also be divided into two (or more) parts.

[0069]FIG. 5 shows a perspective view of the inner ring 33 according toan embodiment of the invention. The inner ring 33 comprises a pluralityof grooves 51. Preferably, two grooves 53, opposite to one another, havea relative larger width than the other grooves. These larger grooves 53are provided to pass the cooling spokes 44, 45. According to embodimentsof the invention, the inner ring 33 is only supported mechanically bythe plurality of lamellas 31, 32 and is not connected to anything otherthan the lamellas 31, 32.

[0070]FIG. 6 shows a detailed example of the lamella 31, 32 of the foiltrap 9 according to an embodiment of the invention. The lamella 31, 32is a very thin platelet having two curved edges 60, 61, a straight outeredge 65, and an inner edge 62 having an indentation 63. The lamella 31,32 has a height h and a width w, see FIG. 6. The outer edge 65 ismechanically connected to the outer ring 35, see FIG. 4. The inner edge62 is inserted into one of the grooves 51 of the inner ring 33, see FIG.5. Preferably, the lamellas 31, 32 are soldered or welded to the outerring 35. In this way, a good thermal contact is provided andapproximately all the heat absorbed by the lamellas, is transported tothe outer ring 35. In one embodiment, the outer ring 35 is cooled by acooling device, not shown, to remove the heat from the foil trap 9.

[0071] In an embodiment of the invention, the foil trap 9 also comprisesa second heat shield in order to block thermal radiation from the firstheat shield 41. FIG. 7 shows a foil trap 9 with first and second heatshields 41, 71. In an embodiment, the second heat shield 71 comprises adisc, positioned inside the inner ring 33 and situated at the back end(i.e. down stream side) of this inner ring 33.

[0072] In another embodiment, the cooling spoke 44, 45, 47 is absent. Inthis case, the first and/or second shields 41, 71 are cooled by acooling device, arranged in a way known by a person skilled in the art.The cooling device may comprise a water cooling system. This watercooling system can be part of a cooling system of the collector 10 ofthe radiation system 3. In this case, the shields 41, 71 are supportedby the cooling device.

[0073] In yet another embodiment, the inner ring 33 is cooled by acooling device. The cooling device for cooling the shields 41, 71 andthe cooling device for cooling the inner ring 33, may be one. The foiltrap 9 may be focused on the radiation source 6. It is also possible toconstruct a foil trap 9 without a real focus. In any case, channels,i.e., spaces between adjacent lamellas, in the foil trap 9 have to bealigned with the emitted EUV beam. In FIG. 2, the foil trap 9 is focusedon the radiation source such that EUV rays of radiation emitted from theEUV source may pass the lamellas 31, 32 without obstruction. Typicalvalues for the dimensions of the lamellas are: height h=30 mm, thickness0.1 mm and width w=50 mm (curved). A typical value for the channelwidth, i.e. the distance between adjacent lamellas, is 1 mm. Thedistance from the foil trap 9 to the source LA is typically in the orderof 60 mm. These specific dimensions are examples and should not beconsidered to be limiting in any way.

[0074] The embodiment of FIG. 8 is similar to the one shown in FIG. 4,except for the additional heat shield 46, mounted in front of shield 41.The additional shield 46 prevents the first shield 41 from beingexcessively heated by direct radiation from the radiation source LA, andconsequently reduces heat radiating from the first shield 41 towards thecollector 10. The additional heat shield 46 may be mounted on shield 41using a dedicated separation device 48 in order to accomplishsubstantially thermal isolation between the two shields. The separationdevice 48 may be manufactured e.g. from ceramics, which is able toresist the heat caused by the radiation impinging on the additionalshield 46 and has a very small heat conduction coefficient. In anotherembodiment of the separation device 48, it may be envisaged that byspecial design of the separation device a heat resistance is createdbetween the additional shield 46 and shield 41 considerably reducingheat transfer between the two shields.

[0075] While specific embodiments of the invention have been describedabove, it will be appreciated that the invention may be practicedotherwise then as described. The description is not intended to limitthe invention.

What is claimed is:
 1. A contamination barrier that passes throughradiation from a radiation source and captures debris coming from theradiation source, said contamination barrier comprising: an inner ring;an outer ring; and a plurality of lamellas extending in a radialdirection from a main axis, each of said lamellas being positioned in arespective plane that comprises said main axis, wherein at least oneouter end of each of said lamellas is slidably connected to at least oneof said inner and outer ring.
 2. A contamination barrier according toclaim 1, wherein said lamellas are thermally connected to at least oneof said inner and outer ring.
 3. A contamination barrier according toclaim 1, further comprising a first shield that protects said inner ringfrom being hit by radiation from said radiation source.
 4. Acontamination barrier according to claim 3, further comprising a secondshield that blocks thermal radiation from said first shield.
 5. Acontamination barrier according to claim 4, further comprising a thirdshield that reduces heating of the first shield caused by directradiation from the radiation source, wherein said third shield isdisposed upstream of said first shield with respect to the direction ofpropagation of the radiation emitted by the radiation source along themain axis.
 6. A contamination barrier according to claim 5, wherein saidthird shield is substantially thermally isolated with respect to saidfirst shield.
 7. A contamination barrier according to claim 6, whereinsaid third shield is connected to said first shield.
 8. A contaminationbarrier according to claim 3, further comprising at least one coolingspoke to support said first shield, said at least one cooling spokebeing thermally connected to said outer ring.
 9. A contamination barrieraccording to claim 8, wherein said first shield comprises a plurality ofshield members, each shield member being connected to said outer ringvia a separate cooling spoke.
 10. A contamination barrier according toclaim 4, further comprising a first cooling device arranged to cool atleast one of said first and second shields.
 11. A contamination barrieraccording to claim 10, further comprising a second cooling devicearranged to cool said inner ring.
 12. A contamination barrier accordingto claim 11, further comprising a third cooling device arranged to coolsaid outer ring.
 13. A contamination barrier according to claim 1,wherein said lamellas are curved in said respective planes, and saidinner and outer ring are shaped as slices of a conical pipe.
 14. Acontamination barrier according to claim 1, wherein a first side of saidlamellas facing the radiation source is thicker than the rest of saidlamellas.
 15. A contamination barrier that passes through radiation froma radiation source and captures debris coming from the radiation source,said contamination barrier comprising: a plurality of lamellas; and asupport structure that slidably engages said lamellas, wherein saidlamellas and said support structure are configured and arranged to allowsaid lamellas to expand and contract in response to changes intemperature.
 16. A contamination barrier according to claim 15, whereinsaid support structure comprises an inner ring and an outer ring andsaid plurality of lamellas are slidably connected to at least one ofsaid inner and outer ring.
 17. A contamination barrier that permitsradiation to pass therethrough and captures debris from a radiationsource generated by the radiation source, said contamination barrierincluding a support structure and a plurality of thin plate membersmounted on said support structure, said radiation propagating along anoptical axis and said thin plate members being disposed along a planethat includes said axis, said plate members being slidably movablerelative to said support structure.
 18. A radiation system comprising: acontamination barrier that passes through radiation from a radiationsource and captures debris coming from the radiation source; and acollector that collects radiation passing said contamination barrier,wherein said contamination barrier comprises an inner ring, an outerring, and a plurality of lamellas extending in a radial direction from amain axis, each of said lamellas being positioned in a respective planethat comprises said main axis, and at least one outer end of each ofsaid lamellas is slidably connected to at least one of said inner andouter ring.
 19. A radiation system comprising: a contamination barrierthat passes through radiation from a radiation source and capturesdebris coming from said radiation source, said contamination barriercomprising a plurality of lamellas; and a collector that collectsradiation passing said contamination barrier, wherein a surface of saidlamellas is covered with the same material as an optical surface of saidcollector.
 20. A lithographic projection apparatus comprising: aradiation system to provide a beam of radiation; a support structure tosupport a patterning structure to be irradiated by a beam of radiationto pattern said beam of radiation; a substrate support to support asubstrate; and a projection system to image an irradiated portion of thepatterning structure onto a target portion of the substrate, whereinsaid radiation system comprises a contamination barrier that passesthrough radiation from a radiation source and captures debris comingfrom the radiation source, said contamination barrier comprising aninner ring, an outer ring, and a plurality of lamellas extending in aradial direction from a main axis, each of said lamellas beingpositioned in a respective plane that comprises said main axis, and atleast one outer end of each of said lamellas is slidably connected to atleast one of said inner and outer ring; and a collector for collectingradiation passing said contamination barrier.
 21. A lithographicprojection apparatus comprising: a radiation system to provide a beam ofradiation; a support structure to support a patterning structure to beirradiated by a beam of radiation to pattern said beam of radiation; asubstrate support to support a substrate; and a projection system toimage an irradiated portion of the patterning structure onto a targetportion of the substrate, wherein said radiation system comprises acontamination barrier for passing through radiation from a radiationsource and for capturing debris coming from said radiation source, saidcontamination barrier comprising a plurality of lamellas; and acollector for collecting radiation passing said contamination barrier,wherein a surface of said lamellas is covered with the same material asan optical surface of said collector.
 22. A method of manufacturing anintegrated structure by a lithographic process, said method comprising:radiating a beam of radiation through a radiation system; providing asupport structure to support a patterning structure to be irradiated bythe beam of radiation to pattern said beam of radiation; providing asubstrate support to support a substrate; and providing a projectionsystem to image an irradiated portion of the patterning structure onto atarget portion of the substrate, wherein said radiating the beam ofradiation through the radiation system comprises passing radiation froma radiation source through a contamination barrier comprising an innerring, an outer ring, and a plurality of lamellas extending in a radialdirection from a main axis, wherein each of said lamellas beingpositioned in a respective plane that comprises said main axis, and atleast one outer end of each of said lamellas is slidably connected to atleast one of said inner and outer ring; and collecting radiation passingsaid contamination barrier.
 23. A method of manufacturing an integratedstructure by a lithographic process, said method comprising: radiating abeam of radiation through a radiation system; providing a supportstructure to support a patterning structure to be irradiated by the beamof radiation to pattern said beam of radiation; providing a substratesupport to support a substrate; and providing a projection system toimage an irradiated portion of the patterning structure onto a targetportion of the substrate, wherein said radiating the beam of radiationthrough the radiation system comprises passing radiation from aradiation source through a contamination barrier comprising a pluralityof lamellas, capturing debris from said radiation source, and collectingradiation passing said contamination barrier with a collector, wherein asurface of said lamellas is covered with the same material as an opticalsurface of said collector.
 24. A method of manufacturing an integratedstructure by a lithographic process, said method comprising: generatinga beam of radiation with a radiation source; capturing debris from theradiation source; collecting radiation passing said contaminationbarrier; patterning said beam of radiation with a patterning structure;and imaging an irradiated portion of the patterning structure onto atarget portion of a substrate, wherein said capturing debris comprisesproviding a support structure and a plurality of lamellas that areslidably engaged with the support structure so as to allow the pluralityof lamellas to expand and contract in response to changes intemperature.